thermometer.ino

const int TEMP_PIN = 0;

const int RED   = 12;
const int GREEN = 13;
const int BLUE  = 11;

void setup() {
  Serial.begin(9600);
  pinMode(RED, OUTPUT);
  pinMode(GREEN, OUTPUT);
  pinMode(BLUE, OUTPUT);
  Serial.println("-----BEGIN-----");
}

void loop() {
  float voltage, temp;
  for (;;) {
    voltage = getVoltage(TEMP_PIN);
    temp = (voltage - 0.5) * 100;
    Serial.print("Temperaure: "); Serial.print(temp); Serial.println("C");
    if (temp < 25)
      lightUp(BLUE);
    else if (temp > 30)
      lightUp(RED);
    else
      lightUp(GREEN);
    delay(500);
  }
}

float getVoltage(int pin) {
  return analogRead(pin) * 0.004882814;
}

void lightUp(int pin) {
  for (int i = 11; i <= 13; i++)
    digitalWrite(i, i==pin?HIGH:LOW);
}